Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
  • G01N21/8914—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the material examined
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/86—Investigating moving sheets
  • G01N2021/8663—Paper, e.g. gloss, moisture content
  • G01N2021/8681—Paper fibre orientation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
  • G01N21/8914—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the material examined
  • G01N2021/8917—Paper, also ondulated

Definitions

• the present invention relates to a method as defined in the preamble of claim 1 and to a device as defined in the preamble of claim 15 for determining fiber orientation in a paper sample.
• 'paper sample 1 refers to weblike products, such as paper, cardboard or other paper industry products, manufactured from lignocellulose based materials.
• Fiber orientation' refers to the orientation of the fibers in a paper sample.
• the fibers are mostly oriented in the machine direction rather than in the transverse direction.
• the degree and angle of fiber orientation vary in relation to the web width, i.e. in the transverse direction of the paper web, and in relation to time, i.e. in the longitudinal direction of the paper web.
• Fiber orientation is generally different in different paper sorts.
• Previously known is a method for determining the mean fiber orientation in a paper sample as a ratio of machine direction tensile strength to transverse direction tensile strength, i.e. as a strength ratio.
• a method for determining mean orienta- tion by measuring the speed of propagation of ultrasound in a web in different directions is known. In this method, the distance lag or sound modular ratio obtained indicates the mean orientation angle and degree.
• Devices suited for implementing the method are manufactured e.g. by Lorentzen & Wet re and Nomura.
• Previously known is also a method for determining mean orientation by optical means.
• a thin round beam of light is directed at the paper surface and the shape of the beam is measured from the other side of the paper.
• the ellipticity of the shape of the beam increases in proportion to the degree of orientation in the sample.
• Instruments for this purpose are manufactured e.g. by Honeywell.
• a problem with the prior-art methods is that only the mean fiber orientation in a certain area in the paper sample can be determined.
• Prior-art methods for determining fiber orientation are difficult to use in practice; for instance, the tensile strength ratio is not easy to determine.
• Tensile strength ratio is not a good measure of fiber orientation in other re- spects, either, because, in addition to fiber orientation, it depends on the drying history of the paper, such as the degree of shrinkage occurring in the web as it is drying.
• a further problem is that prior-art methods are not applicable for the determination of surface orientation (surface orientation refers to fiber orientation at the paper surface) and surface orientation difference between surfaces.
• the object of the invention is to eliminate the problems mentioned above and to disclose a new workable method and device for determining fiber orientation that will be easier to implement in industrial applications.
• a further object of the invention is to disclose a method and device for determining, besides mean fiber orientation, fiber orientation separately for the upper and/or lower surfaces of a paper sample.
• the method and device of the invention are characterized by what is presented in the claims.
• the invention is based on determining fiber orientation in a paper sample.
• the surface of the sample is illuminated from an oblique angle using more than one light source.
• the illumination is ro- tated on the surface of the sample by switching the light sources electronically on and off in turn by means of a switch.
• the intensity of the light reflected from the sample surface is measured by means of at least one sensor and, based on the measured light intensity and momentary direction of illumination, fiber orientation in the sample is determined using a computing device.
• the surface of the sample can be illuminated and/or the intensity of the light reflected from the sample surface can be measured continuously.
• the surface of the sample is illuminated using LED type light sources. If desirable, the sample can be illuminated with polarized or non-polarized light.
• the inten- sity of the light reflected from the surface of the sample is measured using a light emitting diode.
• the light emitting diode is disposed e.g. substantially perpendicularly to the sample surface.
• at least two sensors are disposed substantially in the form of a bar, and the bar is placed in a position substantially perpendicular to the direction of motion of the sample.
• the light sources and sensor are disposed in a substantially unitary assembly, forming a measuring device.
• the device comprises a movable controlling element, the measuring device being placed substantially in conjunction with said controlling element.
• the measuring device as such may be free of movable parts.
• the controlling element may be designed to be movable by a previously known technique, e.g. using a hydraulic device.
• the measurement is performed substantially above and below the sample.
• the sample is a moving web .
• fiber orientation on different surfaces of the sample can be determined separately so that it will be possible to determine separate surface orientations and a surface orientation difference in addition to the mean fiber orientation.
• a further advantage of the invention is that it allows on-line type determination of fiber orientation even from a moving sample and without breaking the sample.
• a further advantage is an insignificant need for maintenance of the measuring device because the measuring device is completely or partially free of movable parts.
• a further advantage is a compact size and simplicity of manufacture of the device.
• the apparatus can be easily added to existing equipment e.g. in paper industry without any substantial changes, thus allowing easy, quick and advantageous implementation of the method.
• a further advantage of the invention is re- producibility and stability of the light intensity measured by the sensor.
• Fig. 1 presents an embodiment of the device of the invention in lateral view
• Fig. 2 and 3 present embodiments of devices according to the invention in top view
• Fig. 4 presents an embodiment of a device according to the invention
• Fig. 5 presents an on-line embodiment of a device according to the invention
• Fig. 6 presents a detail of the embodiment presented in Fig. 5.
• Fig. 1 presents an embodiment of the apparatus of the invention for the measurement of fiber orientation.
• LED-type light sources 2 and 3 are used.
• LED-type light sources can be turned on and off very rapidly without substantial delays.
• the number of light sources is more than one, preferably at least three.
• Fig. 1 shows further that the light sources illuminate the surface of the sample 1 from an oblique angle 11 of e.g. about 45 degrees. It is naturally possible to illuminate the sample surface from angles of other sizes as well.
• the illuminating beam may typically have a small diameter, e.g. below 10 mm.
• the sample in this embodiment is a moving paper web, from whose surface the light is reflected substantially perpendicularly in an upward direction.
• the angle of incidence of the light on the paper surface and the angle of departure of the reflected light from the surface may differ from each other; for instance, the ratio of incidence angle to departure angle is 45°/90°.
• the intensity of the light reflected from the surface is measured using at least one sensor 5, which in the embodiment in Fig. 1 is a light emitting diode, preferably disposed perpendicularly to the sample. The measurement is performed in a measuring area having a diameter below 10 mm.
• the surface of the sample 1 can be illuminated and/or the intensity of the light reflected from the sample surface can be measured continuously.
• Fig. 2 presents an embodiment of the disposi- tion of the light sources 2, 3 and 4 in relation to the sensor 5 as seen from above.
• the light sources can be placed at equal distances in a circular arrangement on the circumference of an imaginary circle e.g. so that the sensor remains at the centre of the light sources in the middle of the circle.
• the light sources can also be disposed in a semicircular arrangement on the circumference of an imaginary circle, e.g. as illustrated in Fig. 3, while the sensor is placed at the centre of the imaginary circle.
• the illumination is rotated on the surface of the sample by turning the light sources on and off successively by means of an electronic switch 12 (Fig. 1) . Since the turn-on time of especially LED-type light sources is very short, a high virtual speed of rotation is achieved without movable parts as light rays proceeding from different directions, i.e. light sources, are turned on and off and the illumination substantially rotates around the spot on the sample surface observed by the sensor. In the device of the invention, it is possible to use any LED-type light sources and electronic switches known in this field, the details of which will not be described in this context .
• the light beam As the light beam is rotated, the light falls on the sample surface from different directions, so it is reflected from the sample surface in different ways depending on the fiber orientation and the direction of the light directed at the fibers. Maximum reflection occurs when the light falls on the fiber perpendicularly from a lateral direction.
• the intensity of the light reflected from the illuminated spot on the surface of a sample to which an illuminating beam is applied alternately from three directions is measured.
• the directional angle and/or degree of fiber/surface orientation On the basis of the measurement or series of measurements of light intensity and the momentary direction of illumination, it is possible to determine the directional angle and/or degree of fiber/surface orientation.
• the determination of fiber/surface orientation can be performed on the basis of the measure- ment results by using a separate computing device, which may be any known computing device 13 (Fig. 1) , which will not be described here in detail.
• a polarizing element 14 (Fig. 1) , e.g. a polarization filter, may be placed in front of each LED-type light source 2 and 3.
• Other solutions for producing polarized light such as a light source producing polarized light directly, can also be utilized in the method.
• nonpolarized light may be used as well.
• Fig. 4 presents an embodiment of the device of the invention.
• the sensors 5 and 6 are mounted in pairs above and below the paper sample 1, the first one 5 of the sensors being placed above the paper sample and the second one 6 above it .
• the sensors are placed against the paper web 1 so that opposite sensors also form a support for the paper web during the measurement, preventing the sample from fluttering in the measuring gap.
• the sensors measure the surface orientation in both surfaces simultane- ously.
• the sensors above and below the sample can be disposed in a stepped manner relative to each other in the direction of motion of the sample as shown in the figure, so that light rays penetrating the paper will not disturb the measurement.
• Fig. 5 shows an on-line embodiment of the device of the invention.
• the measuring device is mounted substantially in conjunction with a movable controlling element 15.
• the sensor 5, light sources 2, 3 and 4, electronic switch 12 and computing device 13 form a substantially unitary measuring device.
• the measuring device may naturally only consist of a sensor and/or light sources.
• the measuring device in itself is preferably free of movable parts, thus reducing the need for maintenance .
• the controlling element 15 held in a measuring position is brought close to the paper sample 1, which is moving e.g. on a rigid cylinder 10 with a large diameter in a paper machine.
• the measuring device does not come into contact with the sample.
• the controlling element can be moved, in this embodiment raised and lowered as necessary.
• the on-line embodiment of the device can be used to measure light intensity from a moving paper sample, such as a web running in the wire section of a paper machine.
• Fig. 6 presents a detail of Fig. 5.
• a sensor bar 8 instead of a single sensor 5, a sensor bar 8, i.e. a measuring device consisting of a number of sensor modules 7, i.e.
• the size of the sensor modules may be e.g. 50 x 100 mm.
• a sensor bar with sensor modules mounted on it can be used for continuous measurement of surface orientation profile across the whole width of a paper web, e.g. with a spacing of 50 mm, for instance to imple- ment accurate monitoring of the effects of adjustments of the headbox lip of the paper machine.
• Each sensor module 7 may naturally comprise light sources, an electronic switch and/or a computing device besides a sensor or sensors.
• the sensor bar 8 may naturally be provided with a given number of light sources and other components of the device of the invention.
• Several sensor bars may be used in con- junction with the device of the invention.
• the intensity of the light reflected from the surface of the paper is measured from both sides of the web 1 using two controlling elements 15 disposed on either side of the web, e.g. substantially in the vicinity of two successive rollers or cylinders so that the first controlling element is above the web and the second one below it.
• Results obtained using the method and device of the invention for determining fiber orientation have been compared with fiber orientations determined using a commercial sound module measuring device.
• the results obtained indicate that the method of the invention and the previously known method of determina- tion correspond to each other.
• the method and device of the invention are applicable as different embodiments for the determination of any fiber orientation, especially surface orientation in a paper web.

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Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (7)

Cited By (6)

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Citations (4)

Family Cites Families (2)

• 1998
  • 1998-06-23 FI FI981443A patent/FI108675B/fi not_active IP Right Cessation
• 1999
  • 1999-06-21 CA CA2334878A patent/CA2334878C/en not_active Expired - Fee Related
  • 1999-06-21 WO PCT/FI1999/000544 patent/WO1999067625A1/fi active Application Filing
  • 1999-06-21 DE DE19983317.6T patent/DE19983317B3/de not_active Expired - Fee Related
  • 1999-06-21 US US09/720,624 patent/US6643022B1/en not_active Expired - Lifetime
  • 1999-06-21 AU AU47867/99A patent/AU4786799A/en not_active Abandoned
• 2000
  • 2000-12-15 SE SE0004643A patent/SE520541C2/sv not_active IP Right Cessation

Patent Citations (4)

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